Frostbite is an injury caused by freezing of the skin and underlying tissues. First your skin becomes very cold and red, then numb, hard and pale. Frostbite is most common on the fingers, toes, nose, ears, cheeks and chin. Exposed skin in cold, windy weather is most vulnerable to frostbite. But frostbite can occur on skin covered by gloves or other clothing.

Frostnip, the first stage of frostbite, doesn't cause permanent skin damage. You can treat very mild frostbite with first-aid measures, including rewarming your skin. All other frostbite requires medical attention because it can damage skin, tissues, muscle and bones. Possible complications of severe frostbite include infection and nerve damage.

Signs and symptoms of frostbite include:

At first, cold skin and a prickling feeling

Numbness

Red, white, bluish-white or grayish-yellow skin

Hard or waxy-looking skin

Clumsiness due to joint and muscle stiffness

Blistering after rewarming, in severe cases

Frostbite is most common on the fingers, toes, nose, ears, cheeks and chin. Because of skin numbness, you may not realize you have frostbite until someone else points it out.

Frostbite occurs in several stages:

Frostnip. The first stage of frostbite is frostnip. With this mild form of frostbite, your skin pales or turns red and feels very cold. Continued exposure leads to prickling and numbness in the affected area. As your skin warms, you may feel pain and tingling. Frostnip doesn't permanently damage the skin.

Superficial frostbite. The second stage of frostbite appears as reddened skin that turns white or pale. The skin may remain soft, but some ice crystals may form in the tissue. Your skin may begin to feel warm — a sign of serious skin involvement. If you treat frostbite with rewarming at this stage, the surface of your skin may appear mottled, blue or purple. And you may notice stinging, burning and swelling. A fluid-filled blister may appear 24 to 36 hours after rewarming the skin.

Severe (deep) frostbite. As frostbite progresses, it affects all layers of the skin, including the tissues that lie below. You may experience numbness, losing all sensation of cold, pain or discomfort in the affected area. Joints or muscles may no longer work. Large blisters form 24 to 48 hours after rewarming. Afterward, the area turns black and hard as the tissue dies.

When to see a doctor

Seek medical attention for frostbite if you experience:

Signs and symptoms of superficial or deep frostbite — such as white or pale skin, numbness, or blisters

Increased pain, swelling, redness or discharge in the area that was frostbitten

Fever

New, unexplained symptoms

Get emergency medical help if you suspect hypothermia, a condition in which your body loses heat faster than it can be produced. Signs and symptoms of hypothermia include:

Intense shivering

Slurred speech

Drowsiness and loss of coordination

Frostbite occurs when skin and underlying tissues freeze. The most common cause of frostbite is exposure to cold-weather conditions. But it can also be caused by direct contact with ice, freezing metals or very cold liquids.

Specific conditions that lead to frostbite include:

Wearing clothing that isn't suitable for the conditions you're in — for example, it doesn't protect against cold, windy or wet weather or it's too tight.

Staying out in the cold and wind too long. Risk increases as air temperature falls below 5 F (minus 15 C), even with low wind speeds. In wind chill of minus 16.6 F (minus 27 C), frostbite can occur on exposed skin in less than 30 minutes.

Touching materials such as ice, cold packs or frozen metal.

The following factors increase the risk of frostbite:

Medical conditions that affect your ability to feel or respond to cold, such as dehydration, exhaustion, diabetes and poor blood flow in your limbs

Alcohol or drug abuse

Smoking

Fear, panic or mental illness, if it inhibits good judgment or hampers your ability to respond to cold

Previous frostbite or cold injury

Being an infant or older adult, both of whom may have a harder time producing and retaining body heat

Gangrene — decay and death of tissue resulting from an interruption of blood flow to the affected area — which can result in amputation

Cold exposure that's severe enough to cause frostbite also can cause hypothermia. When your body temperature drops, your heart, nervous system and other organs don't work correctly. Left untreated, hypothermia eventually leads to complete failure of your heart and respiratory system and to death.

Call your doctor if you suspect you have frostbite or hypothermia. Depending on the severity of your symptoms, you may be told to go to an emergency room.

If you have time before your appointment, use the information below to get ready for your medical evaluation.

What you can do

List any signs and symptoms you're experiencing and for how long. It will help your doctor to have as many details as possible about your cold exposure and to know if your signs and symptoms have changed or progressed.

List your key medical information, including any other conditions with which you've been diagnosed. Also list all medications you're taking, including over-the-counter medications and supplements.

Make a note of the date of your last tetanus shot. Frostbite increases risk of tetanus. If you haven't been vaccinated or if your last shot was more than 10 years ago, your doctor may recommend that you be vaccinated.

List questions to ask your doctor. Being prepared will help you make the most of the time you have with your doctor.

For frostbite, some basic questions to ask your doctor include:

Are tests needed to confirm the diagnosis?

What are my treatment options and the pros and cons for each?

What results can I expect?

What skin care routines do you recommend while the frostbite heals?

What kind of follow-up, if any, should I expect?

What changes in my skin should I look for?

Don't hesitate to ask any other questions that occur to you.

What you can do in the meantime

While you wait for your appointment, take appropriate self-care measures, such as:

Protecting the affected area from further cold

Not walking on frostbitten feet

Reducing pain with ibuprofen (Advil, Motrin IB, others)

Not breaking blisters that may develop

The diagnosis of frostbite is usually apparent based on your signs and symptoms, appearance of your skin, and recent exposure to cold.

Your doctor may conduct tests, such as an X-ray, bone scan or magnetic resonance imaging (MRI) test, to determine the severity of the frostbite and to check if bone or muscle is damaged. Your doctor may also run tests if he or she suspects you have hypothermia, a condition that often occurs with frostbite.

Treatment for frostbite includes first-aid care and medical treatment, depending on the severity of the frostbite. You can treat very mild frostbite (frostnip) with first-aid measures. All other frostbite requires medical attention.

First-aid care

Check for hypothermia. Get emergency medical help if you suspect hypothermia.

Protect your skin from further exposure. If you're outside, warm frostbitten hands by tucking them into your armpits. Protect your face, nose and ears by covering them with dry, gloved hands. Don't rub the affected area and never rub snow on frostbitten skin.

Get out of the cold. Once you're indoors, remove wet clothes.

Gently rewarm frostbitten areas. Soak hands or feet in warm water — 99 to 108 F (37 to 42 C) — for 15 to 30 minutes. If a thermometer isn't available, test the water by placing an uninjured hand or elbow in it — it should feel very warm, not hot.

Don't rewarm frostbitten skin with direct heat, such as a stove, heat lamp, fireplace or heating pad. These can cause burns.

If there's any chance the affected areas will freeze again, don't thaw them. If they're already thawed, wrap them up so that they don't refreeze.

Take pain medicine. If you are in pain, take over-the-counter ibuprofen (Advil, Motrin IB, others) to reduce pain and inflammation.

Don't walk on frostbitten feet or toes if possible. This further damages the tissue.

Know what to expect as skin thaws. If the skin turns red and you feel tingling and burning as it warms, normal blood flow is returning. But seek emergency medical attention if the numbness or pain remains during warming or if blisters develop.

Medical treatment

Rewarming of the skin. If it hasn't been done already, your doctor will rewarm the area using a warm-water bath for 15 to 30 minutes. The skin may turn soft and look red or purple. You may be encouraged to gently move the affected area as it rewarms.

Oral pain medicine. Because the rewarming process can be painful, your doctor will likely give you a drug to ease the pain.

Protecting the injury. Once your skin thaws, your doctor may loosely wrap the area with sterile sheets, towels or dressings to protect the skin. You may need a brace or splint if the bone or muscle is involved. And you may need to elevate the affected area to reduce swelling.

Removal of damaged tissue (debridement). To heal properly, frostbitten skin needs to be free of damaged, dead or infected tissue. To better distinguish between healthy and dead tissue, your doctor may wait one to three months before removing damaged tissue.

Whirlpool therapy. Soaking in a whirlpool bath (hydrotherapy) can aid healing by keeping skin clean and naturally removing dead tissue. You'll be encouraged to gently move the affected area while it is under water.

Clot-busting drugs. You may receive an intravenous injection (IV) of a drug that helps restore blood flow (thrombolytic), such as tissue plasminogen activator (TPA). Studies of people with severe frostbite show that TPA lowers the risk of amputation. But these drugs can cause serious bleeding and are typically used only in the most serious situations and within 24 hours of exposure.

Wound therapy. If you have a complex wound, your doctor might suggest a technique called vacuum-assisted closure therapy to promote healing.

Surgery. In severe cases, surgery or amputation may be necessary to remove the dead or decaying tissue.

Take all medications — antibiotics or pain medicine — as prescribed by your doctor. For milder cases of frostbite, take over-the-counter ibuprofen (Advil, Motrin IB, others) to reduce pain and inflammation.

For superficial frostbite that has been rewarmed, apply aloe vera gel or lotion to the affected area several times a day to reduce inflammation.

Avoid further exposure to cold and wind.

Don't walk on frostbitten feet.

Don't apply direct heat or rub the area.

Don't break blisters that may develop. Blisters act like a bandage. Allow blisters to break on their own.

Frostbite can be prevented. Here are tips to help you stay safe and warm.

Limit time you're outdoors in cold, wet or windy weather. Pay attention to weather forecasts and wind chill readings. In very cold, windy weather, exposed skin can develop frostbite in a matter of minutes.

Dress in several layers of loose, warm clothing. Air trapped between the layers of clothing acts as insulation against the cold. Wear windproof and waterproof outer garments to protect against wind, snow and rain. Choose undergarments that wick moisture away from your skin. Change out of wet clothing — particularly gloves, hats and socks — as soon as possible.

Wear a hat or headband that fully covers your ears. Heavy woolen or windproof materials make the best headwear for cold protection.

Wear mittens rather than gloves. Mittens provide better protection. Or try a thin pair of glove liners made of a wicking material (like polypropylene) under a pair of heavier gloves or mittens.

Watch for signs of frostbite. Early signs of frostbite include red or pale skin, prickling, and numbness.

Plan to protect yourself. When traveling in cold weather, carry emergency supplies and warm clothing in case you become stranded. If you'll be in remote territory, tell others your route and expected return date.

Eat well-balanced meals and stay hydrated. Doing this even before you go out in the cold will help you stay warm. And if you do become cold, drinking warm, sweet beverages, such as hot chocolate, will help you warm up.

Keep moving. Exercise can get the blood flowing and help you stay warm, but don't do it to the point of exhaustion.

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